This invention relates to schottky diodes, and more specifically relates to a novel structure and process of manufacture therefor.
Schottky rectifiers have limited current and junction temperature ratings due to their high reverse current amplitudes at elevated temperatures. Moreover, it has been found that the schottky junction is frequently degraded when the completed wafer or chip is soldered into place. The present invention provides a novel schottky junction device with relatively low reverse current at relatively high junction temperatures, and one which does not degrade during assembly in its housing.
In the conventional schottky device, a layer of material such as palladium, or platinum, or the like is plated onto a semiconductor surface such as an epitaxial silicon surface. The material, say palladium, is then sintered to form palladium silicide and a high work function metal such as molybdenum, tungsten, or tantalum is deposited on the palladium silicide. The high work function material could also be deposited directly on a silicon surface.
Devices of the above type are well known and are described, for example, in any of U.S. Pat. Nos. 3,290,127, 3,457,912; 3,550,260; 3,585,469; 3,636,417; 3,668,481; 3,694,719, 3,841,904; 3,932,880. The properties of palladium and platinum silicide contacts are disclosed in the following articles:
Metallurgical Properties and Electrical Characteristics of Palladium Silicide--Silicon Contacts by C. J. Kircher, Solid State Electronics, 1971 Vol. 14, pp. 507-513;
Planar Millimeter-Wave Epitaxial Silicon Schottky-Barrier Converter Diodes by W. V. T. Rusch, Solid State Electronics, 1968, Vol. 11, pp. 517-525;
Structure and Electrical Characteristics of Epitaxial Palladium Silicide Contacts, etc. by W. D. Buckley et al., Solid State Electronics, 1972, Vol. 15, pp. 1331-1337;
Formation Kinetics and Structure of Pd.sub.2 Si Films on Si, by R. W. Bower et al., Solid State Electronics, 1973, Vol. 16, pp. 1461-1471; and
Pt.sub.2 Si and PtSi Formation with High-Purity Pt Thin Films by Canali et al., Applied Physics Letters, Vol. 31, No. 1, July 1977, pp. 43-45.